1. Field of the Invention
The present invention relates to an encoder which detects an interpolation error of a phase signal.
2. Description of the Related Art
Japanese Patent Laid-Open No. 2004-317411 discloses a correcting apparatus of an absolute value encoder that includes a reference encoder having accuracy higher than that of the absolute value encoder (an encoder that is to be corrected). In a configuration of Japanese Patent Laid-Open No. 2004-317411, the absolute value encoder and the reference encoder are mounted on the same axis, and a corrected value is generated based on a difference of detection position information of the two encoders. Then, correcting a detected value of the absolute encoder using this corrected value, highly-accurate position information can be obtained.
Japanese Patent Laid-Open No. 2001-91237 discloses a generating apparatus of an error correction value that combines a detector being measured and a reference detector and that measures an error based on a difference between a position detection value of the detector being measured and a position detection value of the reference detector so as to generate a corrected value.
However, in the configurations disclosed in Japanese Patent Laid-Open No. 2004-317411 and Japanese Patent Laid-Open No. 2001-91237, a highly-accurate reference encoder is necessary and therefore manufacturing cost of the encoder is increased. In addition, when the encoder being corrected (the detector being measured) and the reference encoder (the reference detector) are attached to each other, a residual error of the error caused by an attachment error may be generated. Furthermore, after these encoders are incorporated, it may be necessary to remove the encoders in order to readjust the corrected value.